This invention relates to an improved lock for a test station apparatus used to couple conductor leads extending from a pipe, a casing, an anode, the soil or the like to a device to measure, supply or respond to an electrical current or potential. More particularly, the present invention relates to a radially-extending L-shaped spring lock supported by a base collar so that a resilient leg overlies the outer side wall surface thereof and projects from the rim portion of a removable cover to permit access for disengagement from the end surface of a thread bar on the cover that is part of a clamping bayonet-type interconnection between the cover and the collar.
Cathodic test stations are typically employed to provide aboveground terminals for convenient monitoring of electrical currents and potentials associated with numerous types of piping, casing and other metallic structures. The test station provides terminals to which the leads are connected for measuring underground structure to soil potentials, cathodic protection anode currents, the resistive integrity of insulation between various types of underground structures such as a pipe, its casing or carrier. Such a test station is also used to direct and measure stray electrical currents in underground or subterranean structures as well as for reading electrical potentials.
One known form of test station apparatus provides a housing made of aluminum material attached to a metal conduit that offers no protection to personnel against electrical shocks and undergoes destructive corrosion. Measures, such as a lock, were not provided to deter or prevent unauthorized access to the terminals enclosed by the test station apparatus. A recent form of known test station apparatus is comprised essentially of plastic material and coupled to the upper end of a conduit or a carrier plate by a collet-type compression fitting. The test station apparatus includes a collar with pedestals to support a terminal block to traverse across an annular opening in the end wall of the collar. The side wall of the collar includes, in addition to a threaded portion for mating engagement with the threads of a collet nut, a separately threaded portion to mate with threads on a dome-like cover. Several different forms of lock structures have been suggested to prevent removal of the cover and unauthorized access to the terminals. One such lock takes the form of a lock bar on the cover that must be passed along a tortuous path of travel formed by projecting walls from the side wall of the collar. Another form of lock takes the form of a bayonet-type connection wherein one of the interlocking lock bars carries a resilient arm with a stop member to engage within a recess that is formed in the cover. A small hole in the cover is provided so that a rod-shaped instrument can be inserted through the hole to contact the stop member and displace it from within the recess. This form of lock is difficult to operate and requires the special use of a rod-shaped instrument. Since the resilient bar is made of plastic material and to provide the necessary strength to achieve the intended locking function, a very substantial force must be imposed by the instrument to move the lock projection from the recess in the cap. Moreover, the plastic material forming the lock member will yield or simply move from a locking relation in the recess of the cover by an excessively large torque applied to the cover. Unauthorized access to the test terminals could not be effectively prevented by these forms of locks.